Spirometer



Spt. 16, 1969 BlRD ETAL 3,467,078

SPIROMETER Filed May 10, 1965 4 Sheets-Sheet 1 INVENTORS Forrest M. Bird Henry L. Pohndort Attorneys Sept. E6, 1969 D ET AL SPIROMETER 4 Sheets-$heet 2 Filed May 10, 1965 I NVEN TORS HQ w M 5% H A L 5 m FHJ M Sept. 16, 1969 F. M. BIRD ET AL SPIROMETER 4 Sheets-Sheet 4 Fig.9

ZZZ @zs-D Attorneys United States Patent 3,467,078 SPIROMETER Forrest M. Bird, Airport Box 970, Palm Springs, Calif. 92262, and Henry L. Pohndorf, 1227 Brewster Drive, El Cerrito, Calif. 94530 Filed May 10, 1965, Ser. No. 454,345 Int. Cl. A61b /08 US. Cl. 1282.08 14 Claims ABSTRACT OF THE DISCLOSURE A spirometer having a bellows disposed in a container. A plurality of valve means permit exhaled air from a patient to enter the expansible bellows. A booster valve and venturi means are provided to pressurize the container during patient inhalation to reset the bellows to its zero point and exhaust the exhaled air in the bellows to atmosphere through a one-way check valve.

This invention relates to a spirometer and more particularly to a spirometer for measuring exhaled tidal volume.

Spirometers heretofore available have had a number of serious disadvantages. For example, a major problem with many of these spirometers is that saturated gases returning from the lung often with a vast aerosol suspension have gummed up the moving mechanical parts of such devices. Other devices have been extremely vulnerable to wet gases. Heated screens utilized to combat the water problem tend to dry out the medications used in pulmonary therapy. In devices using spinning vane and rotary gear meters, the wet expired gases have caused them to overshoot or undershoot correct volume presentations. Devices utilizing a direct displacement principle have been found to produce excessive expiratory resistance. It, therefore, can be seen that there is a need for a new and improved spirometer for measuring expired tidal gas volumes.

In general, it is an object of the present invention to provide a spirometer of the above character which overcomes the above named disadvantages.

Another object of the invention is to provide a spirometer of the above character which automatically resets to zero during inspiration.

Another object of the invention is to provide a spirometer of the above character which is easy to maintain and clean.

Another object of the invention is to provide a spirometer of the above character which provides a simple, relatively straight-forward mechanical means for measuring expired tidal volumes during mechanical ventilation of the lung.

Another object of the invention is to provide a spirometer of the above character which can be readily monitored.

Another object of the invention is to provide a spirometer of the above character which can be used to give audible and visible warnings if changes in resistance or compliance occur.

Another object of the invention is to provide a spirom-.

eter of the above character in which electronic accessories can be readily installed for monitoring and recording volume flow patterns and to act as warning devices.

Another object of the invention is to provide a spirometer of the above character which can be utilized with all types of respirators.

Another object of the invention is to provide a spirometer of the above character which can be utilized for introducing a negative phase to a simple positive phase respirator.

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Another object of the invention is to provide a spirometer of the above character in which the bellows will constantly reset to zero regardless of the inspiratory flow or inspiratory time.

Another object of the invention is to provide a spriometer of the above character which will not alter the flow curve of the inspiratory phase and which is adjustable to ensure raising of the bellows to a predetermined position.

Additional objects and features of the invention will appear from the following description in which the preferred embodiment is set forth in detail in conjunction with the accompanying drawings.

Referring to the drawings:

FIGURE 1 is a side elevational view of a spirometer incorporating the present invention.

FIGURE 2 is a top plan view of the spirometer shown in FIGURE 1.

FIGURE 3 is a cross-sectional view taken along the line 33 of FIGURE 2.

FIGURE 4 is a partial view looking along the line 44 of FIGURE 2.

FIGURE 5 is an enlarged cross-sectional view of the aspirator assembly utilized in the spirometer taken along the line 55 of FIGURE 4.

FIGURE 6 is an enlarged cross-sectional view of the check valve assembly, inlet valve assembly and exhalation valve assembly.

FIGURE 7 is an enlarged cross-sectional view of the inspiratory flow booster valve.

FIGURE 8 is a schematic illustration of the spirometer in a typical application showing the dynamic events occurring during the inspiratory phase of respiration.

FIGURE 9 is a schematic illustration similar to FIG- URE 8 but showing the dynamic events occurring during the expiratory phase of respiration.

In general, the spirometer comprising the present invention consists of a container having its top side open and forming a first chamber. Bellows having a closed bottom side and an open top side is disposed in said container and forms a second chamber. A cover is mounted on the container and serves to close the open top side of the bellows and the container. The cover is provided with an inlet which opens into the chamber within the bellows. An inlet valve assembly is mounted on the inlet and includes a valve member movable between open and closed positions to permit the flow of gases into the chamber in the bellows. An exhaust valve assembly is mounted on the inlet valve assembly and is adapted to be connected to the airway of the patient. It also has a valve member movable between open and closed positions for supplying expired gases from the patient to the inlet valve assembly. A one-way check valve is mounted on the containter and is provided for exhausting expired gases to the atmosphere when the bellows is emptied. An inspiratory booster valve is provided for resetting the bellows to zero.

As shown in the drawings, the spirometer consists of a container assembly 11, a bellows assembly 12, and a cover assembly 13. The container assembly 11 consists of a substantially transparent cylindrical open-ended container 14 which defines a chamber 15. The container 14 is provided with vertical calibrations 16 utilized for a purpose hereinafter described. The container assembly includes means for retaining the cover assembly on the container assembly which consists of socket blocks 18 which are secured on the upper extremity side wall of the container 14 by cap screws 19 and 22. A threaded stem 21 is loosely mounted in a conical recess 20 within each socket block 18 and is retained therein by the cap screw 22 threaded into the side wall of the container 14 and through the socket block into the stem. Threaded thumb lock nuts 23 are threaded onto the threaded stems 21.

The bellows assembly 12 consists of a large bellows 26 which can be formed of any suitable material such as rubber and which is provided with a plurality of convolutions or pleats 27. The bellows 26 is substantially cylindrical with an open upper end and a closed bottom end and defines a chamber 28. The bellows is disposed in the chamber 15 of the container 14. A circular plate 29 is secured to the bottom of the bellows 26 by suitable means such as rivets 30 and washers 31. The upper open end of the bellows 26 is supported on the upper portion of the container 14 by a ring 32 which underlies the top extremity of the bellows and rests in an annular recess 33 provided in the upper portion of the container 14.

The cover assembly 13 consists of a circular cover plate 36 which overlies the top opening in the bellows 26 and closes the top of the container 14. Suitable seating means is provided in the form of a ring 37 of resilient material disposed between the cover plate and the upper edge of the container 14. The cover plate is adapted to be clamped into place by the tilt back thumb lock nuts 23 threaded on the stems 21 as shown particularly in FIGURE 3.

The cover plate assembly includes means for sensing the excursions of the lower extremity of the bellows 26 and consists of a tail piece or foot 41 which rests by virtue of gravity on the bottom wall of the bellows 26. A shaft 42 is mounted in the tail piece 41 and is retained therein by a screw 43. The shaft 42 extends upwardly through a shaft guide member 44 threadedly mounted in the cover 36. An air-tight seal is formed between the shaft guide member 44 and the shaft 42 by a sealing member 46 which is retained in engagement with the shaft 42 and the shaft guide member 44 by a nut 47. A bellows weight 48 is mounted on the shaft 42 for a purpose hereinafter described and is retained in a predetermined position by thumb screw 49.

Means is provided for supporting the spirometer and consists of a support arm 51. The outer end of the support arm is provided with a sleeve 52 which is adapted to be slidably mounted upon a post (not shown) of a support stand. A screw 53 is threaded into the sleeve 52 and has a knob 54 mounted thereon for twining the screw. The other end of the support arm 51 is threaded onto an adapter 56 which has its lower extremity seated upon the conical head 57 of a mounting bolt 58. The adapter 56 is retained on the mounting bolt by a nut 59 which engages the lower side of the conical head 57 and is threaded on the lower extremity of the adapter 56. A pin 61 is threaded into the support arm 51 and has mounted thereon a bellows weight 62. A thumb screw 63 is provided in the bellows weight and is adapted to secure the same to the pin 61. Another pin 64 is mounted intermediate the ends of the support arm 51 and carries a larger bellows weight 66 which is retained thereon by thumb screw 67.

The cover plate 36 is provided with an inlet opening 71 which opens into the chamber 28 enclosed by the bellows 26. A fitting 70 is mounted in the opening 71 and has a one-way check valve assembly 72 mounted therein. The check valve assembly 72 consists of a T-shaped valve body 73 having legs 73a, 73b and 730. The body is provided with a flow passage 74 which extends through legs 74a and 740 and a flow passage 75 in leg 74b which enters passage 74 at right angles thereto. The leg 73a is mounted in the fitting 70 and supports the body 73 with the passage 74 in a vertical position. The body is provided with an annular valve seat 76 in the leg 73b through which the passage 75 extends. A valve member or disc 77 formed of a suitable material, such as plastic, is movable between open and closed positions with respect to the seat 74 and to form a sealing engagement with the same. A valve stem 78 is mounted in the valve member 77 and extends axially of the leg 73b. The valve stem 78 is slidably mounted in a spud 79 threaded into the leg 73a. The spud is provided with a plurality of perforations 80 open to the atmosphere. Means is provided for yieldably urging the valve member 4 77 towards a closed position and consists of a spring 81 coaxially mounted on the valve stem 78 and having one end engaging the valve member 77 and having the other end engaging the spud 79.

An inlet valve assembly 82 is mounted in the leg 73c of the valve body 73 and consists of a valve body 83 formed of a suitable material such as metal. The valve body is provided with a radially extending flange portion 83a which is adapted to seat within the leg 73c. The body is also provided with an integral central portion 83b which has a plurality of circumferentially spaced holes 84 therein which communicate with a main flow passage 85 in the body 83. The valve body is an annular valve also provided with a valve seat 86 on the lower extremity thereof. A valve member 87 is adapted to be moved between open and closed positions in a vertical direction with respect to the seat 86. An O-ring 88 is mounted on the valve member and forms a good seal with the seat 86. The valve member is aflixed to a valve stem 89 which is slidably mounted in the central portion 83b and carries an attraction plate 91. Means is provided for attracting the attraction plate 91 and consists of a magnet 92 of a suitable material, such as Alnico, which is slidably retained in a hole 93 provided in a spud 94 threaded into the upper end of the valve body 83. The magnet 92 is slidably mounted in the hole 93 so that it can be adjusted longitudinally in a vertical direction with respect to the attraction plate 91 to thereby vary the attraction forces applied to the attraction plate and to overcome the force of gravity on the valve member 87. The spud 94 is provided with a plurality of circumferentially spaced holes 96 which communicate with the passages 84.

An exhalation valve assembly 101 is mounted on the inlet valve assembly 82 and consists of a valve body 102. The valve body 102 is provided with an extension 102a which is adapted to fit between the upper end of the valve body 83 of the inlet valve assembly 82 and the upper end of the leg 73c of the valve body 73 of the check valve assembly 72. The valve body 102 is provided with a flow passage 103 and an annular seat 104 through which the flow passage 103 extends. An exhalation valve member 106 is mounted in the body 102 between open and closed positions with respect to the valve seat 104. The valve member 106 is provided with a centrally disposed sleeve 107 and a concentric cylindrical skirt 108. A valve stem guide member 109 is seated within the body 102 and has a valve stein 111 slidably mounted therein. The valve stem 111 is provided with a smaller portion 111a that is square in cross-section to reduce sliding friction and which is disposed in the sleeve 107 of the valve member 106.

Means is provided for yieldably urging the valve member 106 towards a closed position with respect to the seat 104 and consists of a coil spring 112 disposed axially of the valve stem 111 having one end disposed on the outside of the sleeve 107 and engaging the valve member 106 and having the other end disposed in a well 113 provided in the valve stem guide member 109.

Yieldable means which is stronger than the force provided by the coil spring 112 is also mounted on the stem 111 and urges the stem 111 in a direction away from the valve member 106. This yieldable means consists of a coil spring 114 axially disposed on the valve stem 111 and having one end seated in a well 116 provided in the valve stem guide member 109 and having the other end engaging the valve stem 111 as shown.

Additional means is provided for moving the valve stem 111 into a position in which it holds the valve member 106 in a closed position and consists of a diaphragm 118 which has its inner portion engaging the valve stem 111 and has its outer annular portion clamped between the valve stem guide member 109 and a cap 119 threaded into the valve body 102. The cap 119 is provided with a passage 121 which communicates with a passage 122 through nipples 123, 124 provided on the cap.

A relief valve assembly 126 is mounted on extension 102!) of the valve body 102. The relief valve assembly 126 consists of a valve body 127 which is seated within the extension 102b. The valve body 127 is provided with a flow passage 128 which extends through an annular valve seat 129 in the body. A valve member 130, formed of a suitable material such as plastic, is movable between open and closed positions with respect to said valve seat. A valve stem 131 is mounted in the valve member and is slidably mounted in a sleeve 132 mounted on a spud 133 threaded into the valve body 127. The spud 133 is provided with a plurality of circumferentially spaced holes 134 which communicate with the flow passage 128. Means is provided for yieldably urging the valve member 130 into sealing engagement with the valve seat 129 and consists of a spring 136 coaxially mounted on the valve stem 131 and having one end engaging the valve member 130 and having the other end engaging the sleeve 132. A tube adapter 137 is mounted in the body 102 and is connected to a tube 138.

Means is provided for resetting the bellows 26 and emptying the expired gases from the bellows and consists of a reset Venturi assembly 141 mounted on a fitting 142 provided on the side wall of the container 14. The Venturi assembly consists of a body 143 which has a Venturi passage 144 extending therethrough. The body is supported upon the tubular extension 142 by a sleeve 146 which fits over the tubular extension 142 and over the body 143. A nozzle assembly 147 is provided which consists of a support member 148 which is threaded onto a body 143 and which has large openings 149 in its sides (see FIGURE 4). A nozzle 151 is mounted in the support member 148 and has its outlet port 152 disposed in front of the Venturi passage 144 and in axial alignment therewith. The nozzle 151 is provided with a nipple 153 which has a tube 154 mounted thereon.

Means is provided for supplying additional high pressure gas to the reset Venturi and consists of an inspiratory flow booster valve assembly 156. The flow booster assembly 156 is shown particularly in FIGURE 7 and consists of a valve body 157 which has a valve stem 158 slidably mounted in a bore 159. A carrier 161 is mounted on one end of the valve stem 158 and is engaged by one end of a spring 162 disposed in a well 163 provided in an inlet fitting 164 threaded into the valve body 157. The fitting 164 is provided with a passage 166 which is in communication with the well 163. The well 163 opens into a chamber 167 provided in the body. The body 157 is also provided with an annular valve seat 168 which is adapted to be engaged by an O-ring 169 carried by the carrier 161 to establish a sealing relationship between the carrier 161 and the body 157. An outlet nipple 171 is threaded into the valve body and is in communication with a passage 172 provided in the body which communicates with the chamber 167. A plug 173 serves to close otf another passage 174 provided in the valve body 157.

Means is provided for urging the valve stem 158 in a direction to move the carrier 161 out of engagement with the valve seat 168 against the force of the spring 162 and consists of a flexible diaphragm 176 which has its inner portion secured to the valve stem 158 and which has its outer margin clamped between the valve body 157 and a cap 177 threaded into the body. A chamber 178 is formed between the diaphragm 176 and the cap 177 to which gases can be supplied through a fitting 179 provided in the cap 177. The plug 181 closes another hole in the cap 177. Suitable means is provided for sealing the valve stem 158 and consists of an O-ring 182 which is held in place by a washer 183 and a retaining ring 184 mounted in the body 157.

As shown in FIGURE 1, the booster valve assembly 156 is connected to a needle valve assembly 187 by threading the fitting 164 into the needle valve assembly.

The needle valve assembly 187 is mounted in a T-shaped.

cylindrical tube 188. The tube 188 is adapted to be connected to a suitable source of gas under pressure as, for

example, a tank 191 as shown schematically in FIGURES 8 and 9 by a tube 192. The gas under pressure is also connected to a respirator 193 of a suitable type such as one described in Patent No. 3,068,856. The gas is supplied to the respirator from the T-shaped member 188 through a fitting 194. The fitting 194 is threaded into a male adapter 196 which is threaded into a fitting 197 provided on the respirator 193.

The outlet nipple 178 from the booster valve assembly 156 is connected to a T 201 by a tube 202. One leg of the T 201 is connected to the tube 154 which is connected to the reset Venturi assembly 141. The other leg of the T 201 is connected to the tube 203 which is connected to the inlet of an inline nebulizer 204 of the type described in copending application Serial No. 447,852, filed Apr. 13, 1965, now Patent No. 3,353,536. The gases for the patient are supplied from the respirator 193 through a tube 206 to the inlet of the nebulizer 204 and to the output of the nebulizer which is connected by tubing 207 to the patient adapter 208 which, as shown schematically in FIGURES 8 and 9, can be in the form of a tracheotomy fitting. I

The fitting 179 of the booster valve assembly 156 is connected by tubing 211 to nipple 122 of the exhalation valve assembly 101. A tube 212 connects the other nipple 123 of the exhalation valve assembly 101 to a tube 213 connected to the output of the respirator 193 and a tube 214 is connected to a small nebulizer 216 of the type described in Patent No. 3,172,406. The outjut of the netbulizer 216 is connected to the large tube 207 connected to the patient. The patient adapter 208 is connected by the large tube 138 to the adapter 137.

Operation of the spirometer may now be briefly describe das follows. Let it be assumed that the spirometer is in a position in which the bellows are in a fully collapsed state. When they are in this state, they still contain approximately 500 cc. of residual volume as indicated in FIGURE 1. It is for this reason that the zero calibration starts at a point which is substantially below the cover plate 36. The index line for providing readout of the bellows is provided by the bottom plate 29. The volume of gas contained in the chamber 28 within the bellows is given by reading the level of the plate 29 on the scale 16. The bellows 26 is in this fully collapsed position during the inspiratory phase of the respirator.

During the inspiratory phase of the respirator 193, gases are supplied through tube 212 and 213 to the exhalation valve assembly and to the booster valve assembly 156. The supply of gas to the exhalation valve 107 urges the diaphragm 118 to the left as viewed in FIG- URE 6 to move the valve stem 111 against the force of the spring 114 to maintain the valve members 106 in a closed position. In the booster valve assembly 156, the gases serve to urge the diaphragm 176 to the right as viewed in FIGURE 8 against the force of the spring 162 and thus moves the carrier 161 out of engagement with the valve seat 168 to permit relatively high pressure gases to flow from the source 191 through the tube 202 to the large nebulizer 204 to cause the liquid contained in the bottom thereof to be formed into small droplets as shown in FIGURE 8. In addition, the high pressure gases are supplied through the reset Venturi assembly 141. This causes gases to be supplied on the reset Venturi 141. The gases are discharged from the nozzle 151 as a high-velocity jet stream into the Venturi passage 144 which sucks in atmosphere gases through the side openings 149 into the chamber 15 within the container 14. These gases including atmospheric air quickly fill up the chamber 15 within the container and push the bellows 26 upwardly as shown in FIGURE 8.

With the inlet valve 82 closed and the exhalation valve 101 maintained in a closed position, the gases from within the variable chamber 28 of the bellows 26 are exhausted to the atmosphere, as shown in FIGURE 8, through the one-way check valve 72 which is automatically opened when the pressure across the valve member 76 is greater than a predetermined pressure as, for example, 1 cc. of water. During the time that this is occurring, mainstream gases are supplied from the respirator 193 through the tube 206 through the large nebulizer 204 to the tubing 207 to the patient adapter 208, and thence to the patient.

The rate at which the spirometer bellows 26 is reset to zero is determined by the rate of fiow of gases through the Venturi assembly 141 which, in turn, is controlled by the needle valve assembly 187. As soon as the bellows 26 has moved to the zero position, the valve member 77 moves to a closed position.

When sufficient gases have been delivered by the respirator 193 to inflate the lungs of the patient to a desired pressure as, for example, 20 cc. of water, the respirator 193 switches off. In addition to stopping the flow of mainstream gases through the tube 206, the flow of gases through the tube 212 is also stopped to remove the pressure from the exhalation valve assembly and to permit the spring 114 to return the valve stem 111 to the right as viewed in FIGURE 6.

As soon as the gas pressure is removed from the passage 212, it is also removed from the passage 211 so that booster valve assembly 156 moves to a closed position under the force of the spring 162.

As soon as this occurs, the valve member 106 moves to an open position to permit the expired gases passing from the patients lugs through the tube 137 to pass into the inlet valve assembly 82. The magnetic inlet valve assembly 82 is adjusted so that it will open under a predetermined pressure as, for example, 8 cm. of water, which is normally substantially less than the peak inspiratory pressure. Thus, the valve memtber 87 is opened by the expired gases against the attraction provided by the magnet 92 on the attraction plate 91. The valve member 87, therefore, drops downwardly and when it is in its extreme open position, it is attracted by the magnet 92 with a force which is substantially less than the force when the valve member 87 is in a closed position as, for example, 1 cm. of water.

Thus, it can be seen that upon initiation of the exhalation phase as shown in FIGURE 9, the inlet valve assembly 82 opens very rapidly so that the expired gases can pass through the inlet valve down into the chamber 28 within hte bellows 26. The bellows descend as the variable chamber defined by the bellows is filled and this continues until the exhalation phase is completed. As soon as the pressure during the exhalation phase is reduced to a predetermined small value as, for example, 1 cm. of water, the attraction by the magnet 92 will overcome the flow of gases through the holes 94 and will move the valve member 87 to a closed position and to thereby seal the ballows chamber so that the physician or other attendant can make a reading on the scale 16 on the container to thereby obtain a determination of the tidal volume of the expired gases from one breath of the patient.

Since the magnetic inlet valve closes at the end of the exhalation phase, this prevents the bellows 26 from descending any further or from creating negative pressures which, in turn, could trigger the respirator 193 which normally should be triggered by the patient. The patient, during inspiration, creates a slight amount of negativity in the breathing circuit which causes the respirator to switch to the inspiratory phase. If the magnetic inlet valve were not utilized, the spirometer would have a tendency to make the breathing cycle for the patient very erratic. This is because the spirometer would cause the respirator to switch prematurely to the inspiratory phase because of the negative pressure created by the bellows 26.

From the foregoing, it can be seen that the reset Venturi means serves as means to empty the expired gases from the bellows which were collected during the previous expiratory phase and also to reset the bellows to zero. As soon as the bellows has been moved to zero position, the valve member 77 is moved to a closed position under the urging of the spring 81. The spirometer is now ready to commence another cycle on termination of the inspiratory phase as hereinbefore described. The relief valve assembly 126 is provided to relieve any undue pressures which may be created in the mainstream flow of gases to the patient.

In other words, it can be stated that the magnetic inlet valve is designed to open at a negative pressure slightly above the maximum negative pressure created within the bellows by the influence of gravity upon the bellows in a fully collapsed up position. The magnetic inlet valve assembly 82 permits negative pressures created within the bellows from being transmitted to the respirator. It also locks the bellows at the end of exhalation for a direct volumetric reading. As pointed out previously, the magnetic inlet valve assembly opens and is designed to remain open until pressure differentials across the gate equal approximately 1 cm. of water. This difference between the initial opening pressure and the terminal closing pressure virtually eliminates expiratory resistance, prevents negative proximal airway pressures, and restrains the respirator that is assisting spontaneous respirator from being prematurely triggered into the inspiratory phase.

Both the inlet valve assembly 82 and the outlet valve assembly 72 are designed so as to eliminate chatter which could cause erroneous readings.

As hereinbefore stated, means is provided whereby the excursions of the bellows can be monitored electrically. This consists of the shaft 42 which is provided with the foot 41 which serves as a cam follower and follows the movements of the lower extremity of the bellows as it moves up and down. Since the shaft moves in this manner, it can be connected to suitable electronic measuring devices or alarm systems such as a switch assembly 171 (see FIGURE 2).

By attaching weights to the shaft 42, it is possible to cause the spirometer to create a mechanical negative pressure against the patients airway within physiological limits for any initial part of the expiratory phase. It is for this reason that the weights 41, 48, 62 and 66 are provided. The weight of the additional mass placed upon the translatory shaft 42 is transmitted to the bottom of the bellows which, in turn, increases the amount of negative pressure being created within the chamber in the bellows. By way of example, a weight of 500 cc. placed on the shaft 42 would have the following effect. If the bellows created at .5 cm. of water negatively in the collapsed position, with the yield pressure of the magnetic inlet valve 82 set at 5.5 cm. of water, the bellows would remain in the collapsed position. When exhaled gas is applied at a pressure of .5 cm. of water against the magnetic inlet valve, the magnetic inlet valve would move to the open position and would remain open until pressure differentials across the valve became less than 1 cm. of water. If the 500 cc. counterweight is added to the translatory shaft 42, negativity within the bellows would exceed the 5.5 cm. of water opening pressure in the inlet valve. The inlet valve would open and admit gases at ambient pressures until the bellows came to rest at the 500 cc. level. A subambient force would be allowed to cross the magnetic inlet valve until 500 cc. of ambient gas has been entrained. If the person receiving mechanical ventilation were set to receive a tidal volume of 1000 cc. and the 500 cc. counterweight were in place, a subambient gradient would exist into the bellows during the first half of the expiratory phase. This would lower the expirator resistance during the period of rapid air flow from the lung with desirable physiological consequences.

It is apparent from the foregoing that we have provided a new and improved spirometer which provides a simple, straight-forward mechanical means for measuring expired tidal volumes during mechanical ventilation of the lung of the patient. The spirometer is particularly adaptable for long-term intensive care procedures in hospitals where patients are being treated for tetanus or barbituate poisoning, crushed chests, and other situations where there is a respiratory insufiiciency. The spirometer is particularly useful for treating patients having obstructed lung disease or which gather secretions from surgical procedures because of the ability to introduce a mechanical negative phase during expiration to reduce expiratory airway resistances. This, in eifect, tilts the pressure gradient from the patient to the atmosphere or bellows to make the flow of the air molecules easier and possibly more rapid. The use of negativity during expiration also has other physiological advantages well known to those skilled in the art.

The spirometer is also one which can be readily cleaned and maintained. The bellows can be readily removed merely by loosening the thumb lock nuts 23 and swiveling them to an out-of-the-way position to remove the cover plate 36. Thereafter, the bellows 26 can be readily removed and cleaned.

The spirometer is also advantageous because it includes inspiratory flow booster valve means for assuring that the bellows will always reset to zero and helps to ensure that the spirometer will not alter the flow curve of the inspiratory phase. The small difference between initial opening pressure and the terminal closing pressure virtually eliminates inspiratory resistance, permits negative proximal airway pressure, and restrains the breathing valve that is assisting spontaneous respiration from being prematurely triggered into the inspiratory phase.

The spirometer is particularly advantageous in that it can be used with any type of respirator and, in particular, can be used with a simple positive phase respirator to accomplish the same purpose as a more expensive positivenegative phase respirator.

We claim:

1. In a spirometer, a container having an open top side forming a first chamber, a bellows having a closed lower side and an open top side disposed in the container and forming a second chamber, removable cover means mounted on said container and serving to close the open top sides of the said bellows and said container, the cover means being provided with an inlet opening into the second chamber in the bellows, an inlet valve assembly mounted on the inlet and having a valve member movable between open and closed positions to permit expired gases to pass into the second chamber in the bellows, an exhaust valve assembly mounted on the inlet valve as sembly and having a valve member movable between open and closed positions, said exhaust valve assembly being adapted to be connected to the airway of the patient to permit expired gases from the patient to pass from the exhaust valve into the inlet valve assembly, and one-way check valve means mounted on the container to permit expired gases from the second chamber in the bellows to be discharged therefrom.

2. A spirometer as in claim-1 together with a translatory shaft slidably mounted on the cover means and engaging the bottom side of the bellows and moving with the bottom side of the bellows, and a weight mounted on said translatory shaft outside of the second chamber formed by the bellows and above the cover means.

3. In a spirometer, a bellows forming a chamber, a container enclosing said bellows and forming a second chamber about the bellows, the bellows having a movable lower end to vary the capacity of the chamber in the bellows, the container having an inlet opening into the bellows, a valve body mounted on the inlet and having a flow passage therein, the valve body being formed with a valve seat through which the flow passage extends, a valve member mounted in said body for movement between open and closed positions with respect to said seat, a valve stem carried by the valve member, an attraction plate mounted on the valve stem, and a magnet mounted in said body and serving to yieldably retain said valve member in a closed position, an exhaust valve assembly adapted to be connected to the airway of the patient and supplying the expired gases from the patient to the inlet valve, and a one-way check valve mounted on said container for exhausting expired gases to the atmosphere when the chamber formed by the bellows is emptied.

4. A spirometer as in claim 3 together with a translatory shaft slidably mounted in said container and following said bellows and giving an indication of the position of said bellows in said container.

5. A spirometer as in claim 3 wherein said valve member is mounted for movement in a vertical direction and wherein said magnet is disposed to apply forces to the attraction plate in a vertical direction to oppose the force of gravity on the valve member.

6. A spirometer as in claim 5 wherein said magnet is adjustable longitudinally in a vertical direction with resepct to the valve member to vary the attractive forces applied to the attraction plate.

7. In a spirometer, a container having an open upper side and defining an open-ended first chamber, bellows having an open upper side and defining an open ended second chamber, said bellows being disposed within the container and having its upper extremity secured to the upper extremity of the container, the bellows having a lower movable end to vary the capacity of the second chamber from a zero position to a fully extended position, a cover closing the open sides of said container and said bellows, said cover being formed with an inlet, an inlet valve body mounted on said cover and having a flow passage therein in communication with the inlet in said cover, said valve body having an annular seating surface disposed in said flow passage, a valve member mounted in said body for movement between open and closed positions with respect to said seat, a valve stem carried by the valve member, means in said valve body slidably mounting said valve stem, an attraction plate mounted on the valve stem, and a magnet mounted in said body and serving to yieldably retain said valve member in a closed position, an exhaust valve assembly adapted to be connected to the airway of the patient and supplying the expired gases to the inlet valve to cause the inlet valve to open against the force of the magnet and to permit the gases to enter the chamber defined by the bellows, and one-way check valve means mounted on the container and adapted to empty the expired gases to the atmosphere.

8. A spirometer as in claim 7 together with means mounted on the container for supplying gas to the first chamber in the container to empty the expired gases from the bellows through the one-way check valve means.

9. A spirometer as in claim 7 wherein said valve stem is disposed in a vertical position so that the force of gravity acts in a direction which is opposite to the direction applied by the attraction forces of the magnet.

10. A spirometer as in claim 9 wherein the magnet is adjustable longitudinally of the valve stem in a vertical direction to vary the attraction forces applied to the attraction plate.

11. A spirometer as in claim 7 together with reset Venturi means mounted on said container, said Venturi means having a Venturi and a nozzle adapted to supply a jet of gases to the Venturi to cause the gases to suck in atmospheric air into the chamber in the container and to move the bellows to discharge the expired gases through the one-way check valve means to the zero position.

12. A spirometer as in claim 11 together with an inspiratory flow booster valve connected to said reset Venturi, means supplying gases under pressure to said booster valve assembly, and means for controlling said booster valve assembly so that it is in an open position during the time that gases are being inspired by the patient.

13. A spirometer as in claim 12 wherein said booster valve assembly consists of a valve body, a valve stem mounted in the body, said valve stem being movable between open and closed positions to control the flow of gases from said source to said reset Venturi means, a diaphragm disposed in said valve body and connected to said valve stem and wherein said means for controlling said booster valve supplies gas under pressure to said diaphragm to move said valve stem to an open position.

14. In a spirometer, a container forming a first chamber, a bellows disposed within said container and forming a second chamber within said first chamber, inlet valve means mounted on said container allowing exhaled gases to enter said second chamber, exhalation valve means mounted on said container and in communication with said second chamber, the inlet valve means being adapted to be connected to the airway of the patient, one-way check valve means mounted on the countainer permitting expired gases in said second chamber to be discharged therefrom, reset Venturi means mounted on the container and in communication with the first chamber, booster valve means connected to said reset Venturi means and movable between open and closed positions, means for supplying gas under pressure to said booster valve means, and means moving said booster valve means to an open position.

References Cited UNITED STATES PATENTS RICHARD A. GAUDET, Primary Examiner KYLE L. HOWELL, \Assistant Examiner US. Cl. X.R. 128145.6 

